Legal Guarding Position

[RefBob]

I came across NFHS Case Book scenario 10.6.1, Situation A with a result that I was not expecting. In the scenario, B1 is legally occupying a spot on the court before A1 jumps in the air to catch a pass. B1 then moves to a new spot (while A1 is airborne). A1 then lands on one foot and charges into B1. Foul on A1.

CB 10.6.1 Situation C has a scenario with airborne shooter A1 with language that says if B1 moves into the path of A1 after A1 has left the floor, the foul is on B1.

Why the different results? I know that in Situation A, A1 is not a shooter, but NFHS Rules 4-23-4b and 4-23-5d seem to have the same language for establishing a legal guarding position on an airborne opponent with or without the ball - "the guard must have obtained legal position before the opponent left the floor."

Not sure what I'm missing.

Thanks.